1. Field of the Invention
The invention relates to connecting mobile subscribers in a cellular radiotelephone network to the public switched telephone network.
2. Description of the Related Art
An article by G. Soderholm, J. Widmark, and E. Ornulf entitled "Ericsson Cellular Mobile Telephone Systems" published in Ericsson Review, No. B 1987, pp. 42 to 49, describes a connection system for mobile subscribers in which radio links are provided by allocating a frequency to a subscriber for the duration of a call.
In this system, function specific both to managing the mobile subscribers and to telephone switching (voice and data) are integrated in the same unit.
An article by P. Duplessis and F. Maillard, entitled "Le systeme cellulaire numerique paneuropeen de radiotelephonie avec les mobiles" (the Pan-Eueropean Digital Cellular System for Radiotelephony with Mobiles) published in Commutation et Transmission, No. 2, 1988, pp. 5 to 14, describes a mobile subscriber connection system in which radio links are provided using the time division multiple access (DTMA) method. In this system, management functions relating to the mobility of mobile subscribers and functions specific to communication are processed in the same unit.
In both of these systems, the same exchange handles both switching functions ad processing functions specific to the mobility of the subscribers. This integration suffers from several drawbacks:
it requires special exchanges to be used;
the exchange requires very considerable processing capacity which is highly sensitive to subscriber mobility and to the topology of the cellular network;
the processing power required for signalling is very largely related to aspects of subscriber mobility, without any bearing on switching functions; and
two applications are mixed up in a single physical system which gives rise to difficulties in the management, maintenance, and updating of each of the applications.
The object of the invention is to avoid the drawbacks of known systems.